1. Field of the Disclosure
The present disclosure relates to a storage device which includes a NAND type flash memory and which is suitable for being used as a Solid State Drive (SSD).
2. Description of the Related Art
In recent years, an SSD has been adopted in a use application in which the SSD has been substituted as a storage device in a Personal Computer (PC) for a Hard Disc Drive (HDD) because the SSD has advantages that an access speed is high and power consumption is less as compared with the case of the HDD. In addition, the HDD is used not only in the PC, but also as a storage device of a built-in apparatus, and the number of cases where the SSD is adopted in the built-in apparatus as well has been increased.
A multi-function printer (hereinafter suitably referred to as “an MFP” in some cases) is known as an example of such a built-in apparatus. The multi-function printer is such that functions of a printer, a facsimile, a scanner, a copy machine, and the like are collected in one apparatus. In the MFP, a manuscript which a user, for example, desires to copy is placed on a platen, and the manuscript placed on the platen is scanned. Thus, data obtained through the scanning (hereinafter simply referred to as “scan data”) is temporarily stored in a storage device such as an HDD for subsequent processing/work. Moreover, jobs such as printing and transmission with a facsimile are carried out based on the data thus scanned.
In such an MFP, the scan data which has been used after completion of the jobs such as the printing needs to be erased from the HDD in order to ensure the security. In the existing MFP using the HDD as the storage device, data to be overwritten such as pieces of data which are all “0,” pieces of data which are all “1,” or data having a predetermined pattern containing therein random numbers is overwritten to the scan data, thereby erasing the scan data.
When the SSD is substituted for the HDD mounted to the MFP, an MFP main body side gives an instruction to overwrite the data to be overwritten to the scan data in the manner as described above, thereby giving an instruction to erase the scan data. However, the NAND type flash memory is used as a storage medium of the SSD in the SSD in many cases. Thus, since it may be impossible for the NAND type flash memory to carry out a direct overwriting operation, there is required a time-consuming operation for writing the data to be overwritten to a block in which the scan data is stored after an erasing operation has been carried out for the block. In addition, in the NAND type flash memory, there is a given limit to the number of times of rewrite. As a result, it is possible that the operation described above is repetitively carried out, thereby shortening the life of the NAND type flash memory.
In the light of such problems, there is proposed an MFP which issues an erasing command from an MPF main body side to an SSD and carries out an erasing operation for a block in which the scan data is stored in accordance with the erasing command. This technique about the MFP, for example, is proposed in Japanese Patent No. 4,340,327.
However, in the existing MFP described above, the MFP main body prepares the unique erasing command for the specific block of the SSD. Also, the SSD carries out the erasing operation for the corresponding block in response to that the erasing command has been issued from the MFP main body. Generally, the HDD cannot carry out the operation for collectively erasing the data in the specific area. Accordingly, for the purpose of erasing the data, the data to be overwritten described above are written to the data in the specific area to carry out the data erasing operation. Therefore, in an interface having general versatility through which the HDD and a host apparatus such as the MFP main body are connected to each other, for example, in an AT Attachment (ATA) or an Small Computer System Interface (SCSI), no erasing command is prepared, and thus the overwrite erasing is carried out by using a normal data write command. For this reason, in the existing MFP described above, it is necessary to prepare a (vendor-dependent) erasing command peculiar to the MFP in order to carry out the SSD erasing operation. Therefore, a special specification change is required for the MFP main body.
The present disclosure has been made in the light of the problems described above, and it is therefore desirable to provide a storage device which is capable of being substituted for a versatile HDD without subjecting a host apparatus to a special specification change.